{"id":"CVE-2026-77255","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-77255","generatedAt":"2026-10-28T01:39:37.528Z","title":"A caller can make the MCP server read arbitrary local files and attach them to a Jira issue, using the server as a confused deputy to exfiltrate the contents.","description":"MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, the Jira update_issue attachments argument is converted into local paths and routed to the attachment upload implementation without workspace validation. A caller can make the MCP server read arbitrary local files and attach them to a Jira issue, using the server as a confused deputy to exfiltrate the contents. The advisory traces the vulnerable input and processing flow through jira update_issue, attachments, upload_attachment, and file_path, which identify the affected entry points, controls, and code paths. This issue is fixed in version 0.22.0.","published":"2026-09-22T19:16:50.000Z","lastModified":"2026-09-29T13:41:25.000Z","status":"Analyzed","sourceIdentifier":"security-advisories@github.com","cvss":{"version":"3.1","score":8.6,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N"},"cwe":["CWE-22","CWE-441"],"affected":["mcp-atlassian/mcp atlassian"],"epss":{"score":0.00459,"percentile":0.39539,"date":"2026-10-26","history":[{"date":"2026-09-23","score":0.00514,"percentile":0.4279}]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (0.46%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[{"kind":"new","label":"New CVE","at":"2026-09-22T19:16:50.000Z","detail":{"score":"8.6","severity":"HIGH","publishedAt":"2026-09-22T19:16:49.850Z"},"summary":"New CVE, high severity (CVSS 8.6)."}],"references":[{"url":"https://github.com/sooperset/mcp-atlassian/commit/b041733473f95119dd539542a43c280737a8e460","tags":["Patch"],"source":"security-advisories@github.com"},{"url":"https://github.com/sooperset/mcp-atlassian/pull/1448","tags":["Issue Tracking","Patch"],"source":"security-advisories@github.com"},{"url":"https://github.com/sooperset/mcp-atlassian/releases/tag/v0.22.0","tags":["Release Notes"],"source":"security-advisories@github.com"},{"url":"https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-2xj6-xx86-cwwc","tags":["Exploit","Vendor Advisory"],"source":"security-advisories@github.com"},{"url":"https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-2xj6-xx86-cwwc","tags":["Exploit","Vendor Advisory"],"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-77255","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}